Milk enzymes

Establishment of the presence of enzymes in milk and their activity levels has been studied ever since systematic research in enzymology came. Milk has enzymes from all the six classes of enzymes. However, majority of enzymes belongs to oxidoreductases, transferases, and hydrolases classes. There are about 63 enzymes. Most commonly studied enzymes in milk are plasmin, lipoprotein lipase, alkaline phosphatase, acid phosphatase, ribonuclease, lactoperoxidase, catalase, xanthine oxidase, superoxide dismutase, sulfhydryl oxidase, γ-glutamyl transpeptidase, N-acetyl-β-d-glucosaminidase, and lysozyme. These enzymes are either present at sufficient concentration in milk or are of technological significance in dairy science and milk processing. Relationship between thermal stability of alkaline phosphatase and heat treatment conditions used during milk pasteurization is exploited for judging proper pasteurization. Understanding of milk enzymology has helped in figuring out causes of milk deterioration during milk processing and storage. The chapter has brought forward the properties of prevalent enzymes in bovine milk as well as comparative information available for milks of buffalo, goat, sheep, camel, and human origin.